1. Field of the Invention:
The present invention relates to an induction immersion pump for hot liquid metals, especially for aluminum, having a channel or canal being immersed in the liquid and having a rectangular cross section, a comb-shaped coil core having teeth pointing toward the channel, and induction coils disposed on the coil core outside the wide sides of the channel. Many embodiments of induction pumps for liquid metals are known, in particular those which have a liquid-metal canal with a rectangular cross section that is disposed between magnet frames with comb-like profiles and coil assemblies mounted thereon. It is therefore an objective of the invention to improve such a pump for use as an immersion pump.
2. Description of the Prior Art:
At present, two methods are mainly used for taking liquid metal from a container, continuously or by the batch. One possibility is ladling over the edge of the container, but manual labor or elaborate mechanisms are necessary therefor. The second possibility is controlled drainage through an opening at the bottom of the melt container. The control is exercised in such a case by a slider or even an electromagnetic pump apparatus. However, if the shut off device fails, there is the risk of emptying the container, for which reason openings below the liquid level in larger containers should be dispensed with. An immersion pump combines the advantages of both methods. It is immersed from above into the melt and pumps the liquid metal continuously or by the batch over the edge of the container.
In the event of a failure, such as due to a power failure, only the pumping is interrupted. An electromagnetic immersion pump can be remotely controlled and permits accurate metering.
In earlier attempts to construct induction pumps for liquid aluminum as immersion pumps, for example, it was impossible to obtain satisfactory results. The reasons therefor are as follows
(a) Because of the high temperatures which naturally occur at the coils in immersion pumps for hot fluids, the windings had to be made of a temperature-resistant material, which led to large losses because of the poor conductivity of such materials. If copper was used as coil material, a lower loss was obtained, but the coils would oxidize at this temperature and would become unusable after a short time.
(b) It was impossible to maintain the magnetic properties of the coil core, depending on the operating condition, since the Curie temperature in the vicinity of the pumping canal was exceeded.
(c) In pumping of aluminum, it was impossible to obtain an aluminum jet free of bubbles, which would be desirable for a sensible employment of immersion pumps.